This invention relates to industrial trucks, such as fork-lift trucks or the like in which it is desirable to control automatically the extent of an auxiliary movement such as the height to which a load is raised.
Conventionally, a fork-lift truck is generally equipped with control levers positioned adjacent to the operator's seat so as to control the height of a fork and/or the tilt angle of a mast thereby. Therefore it requires a great skill to correctly raise the fork to a preselected desirable position by the manipulation of the control levers.
This is especially so when the operator must raise the fork to a high level in order to move loads positioned on a high rack because it is difficult for the operator to see the tip of the fork when it is raised. Since the operator is continuously under severe stress when working, he would likely to be fatigued early and working efficiency would be reduced significantly.
There have been known some fork-lift trucks in which the lifting operation of the fork is controlled by pushing buttons arranged adjacent to the operator's seat instead of manipulating control levers. Most of these prior art devices, however, are not sophisticated enough to effect precise controls of the fork.